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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 03, 2017 through May 18, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
A measured volume of inoculated mineral medium, containing a known concentration of test substance as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (± 1°C) for up to 28 days. Evolved carbon dioxide is absorbed in sodium hydroxide pellets. The consumption of oxygen is determined by measuring the pressure drop in the respirometer flask. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbon is oxidized to carbon dioxide, hydrogen to water and nitrogen to ammonium, nitrite or nitrate).
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Specific details on test material used for the study:
Lot No. VE00466805
Purity : 93.5% (sum of 2 isomers)
Expiry Date : 23 January 2019

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used.

The incubation was continued until 61 days.

The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
Duration of test (contact time):
61 d
Initial test substance concentration
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Preparation of the Flasks :
Test substance samples (13.10 mg, corresponding to 30.0 mg/l in 437 ml of test medium) are weighed in small aluminium boats and added directly to the test flasks of the Oxitop. For reference substance samples 43.70 mg (corresponding to 100.0 mg/l in 437 ml of test medium) are weighed in small aluminium boats and added directly to the test flasks of the Oxitop.

Flasks are filled with 432 ml of mineral medium. Samples of test or reference substance are added. Then 5.00 ml of suspended sludge diluted to a concentration of 2.62 g/l dry matter is added. Except when the test substance has an acid or alkaline character, the pH of each flask is not measured but assumed to be the same as the mineral medium, in order not to remove any floating undissolved test substance from the test medium by dipping a glass electrode in it. Neutral test substances, even sodium benzoate, were shown not to affect the pH of the medium by more than 0.1 pH unit. Two sodium hydroxide pellets are placed in the quivers on top of the bottle, and the flasks are closed tightly with the measuring heads. The flasks are allowed to equilibrate to the test temperature. The measurement is started by programming the measuring unit of the Oxitop test flasks, and the test flasks are placed in the temperature controlled cupboard of the Oxitop system. After temperature equilibration, the controller of the instrument starts the data acquisition (time zero of the experiment).

Performance of the Test :
Everyday the oxygen consumption of each flask is recorded and correct temperature and stirring are checked.

At the end of the test period, the pH of each flask is measured again.

Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
Test concentration 100 mg/L

Results and discussion

Test performance:
The incubation was continued until 61 days.
% Degradationopen allclose all
Key result
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
72
Sampling time:
42 d
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
61 d

BOD5 / COD results

Results with reference substance:
Results with Reference Substance - Sodium Benzoate :
Day 7 72%
Day 14 77%

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
GR-50-3010 should be regarded as readily biodegradable according to this test based on the biodegradation percentage of 66% at day 28.
Executive summary:

GR-50-3010 should be regarded as readily biodegradable according to this test based on the biodegradation percentage of 66% at day 28.